Maintaining correct piston head o-ring size

[PeteJC21]

Hi,
Took my HK53 out the weekend and on getting it chrono'd it came up at around 270fps, a little disappointing considering I just put a Systema M100 spring in it!

I figured it was probably due to crap airseal. I just stripped it down and did the finger over the nozzle and press the piston into the cylinder test and sure enough I was able to push the piston all the way into the cylinder (fairly easily too). I have taped around the cylinder head with ptfe tape & siliconed it and I re-stretched the piston head o-ring by following a top I saw on another airsoft site, by wrapping it around the cylinder and gently heating it, before letting it cool, lubing it with silicone and replacing it on the piston head. Results were great, now have a perfect airseal and I can barely push the piston into the cylinder more than a cm.

However. I read that this method of re-stretching the o-ring to improve airseal is probably only a temporary thing and it will gradually shrink again. So my question is, how do you maintain the correct piston head o-ring size, i.e. prevent it from shrinking and losing your airseal again?

I don't want to crack open the gearbox all the time. Ideally I want to treat it with something that will last a while. Will silicone grease do this?

Thanks
Pete

[dave38x]

Re: Maintaining correct piston head o-ring size

Best way would be to measure the inner diameter of the cylinder, work out how fat an o-ring you want, go on ebay and buy ten of them :P

[mightyjebus]

Re: Maintaining correct piston head o-ring size

the even easier way is to use some plumbers tape (the white PTFE stuff). It costs about £1.50 for a roll and will last you about 300 AEG's. Remove the O ring from the piston head and put a few layers of the tape in the space where the O ring normally sits. Put the O ring back on and test the airseal. repeat until the air seal is good.

[PeteJC21]

Re: Maintaining correct piston head o-ring size

Hmm, not a bad idea idea, didn't think of that. I'll see how long the o-ring lasts. When I start to lose fps again I'll test the airseal and if the o-ring has shrunk again will try this.

Thanks.